Method and device for transmitting data on traffic assessment

ABSTRACT

A process for the wireless transmission of data to a traffic sensor for assessing traffic in segments of a road network includes collecting data in a plurality of floating cars that travel in traffic and have sensor system for collecting the data. A current driving profile is formed in each floating car from the collected data. Actual values of characteristic driving profile properties are derived from the current driving profile and expected values of the characteristic driving profile properties are formed based on preestablished traffic situation information. A difference between the actual values and the expected values is determined and if the difference is determined to be a serious deviation from the expected values based on preestablished decision criteria, the data collected by the sensors is transmitted to a traffic center.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process for the wireless transmission of datato a traffic center for the purpose of assessing traffic in segments ofa road network. The data are collected in a plurality of vehicles(floating cars) that travel in traffic and are equipped with sensorsystems for data collection. The invention also relates to a device toimplement this process.

2. Description of the Prior Art

Various methods are known for the metrological collection of data fortraffic assessment in segments of a road network. Often, stationary orfixed sensors installed at roadside such, for example as inductionloops, are used at especially critical locations to measure technicaltraffic variables, such as the number of vehicles passing during a giventime period or the average speed of these vehicles. However, installingstationary sensors such as those disclosed in U.S. Pat. No. 5,317,311 atroadside or in the road surface is expensive, as is the maintenance ofsuch sensors. As a rule, such sensors transmit current measurement datato a traffic center for further assessment at regular intervals.

Recently, there has been discussion and testing of processes in whichdata measurement for traffic assessment is conducted in the vehiclestaking part in traffic. The vehicles used for this purpose are equippedwith sensors. Such sensor vehicles are also called “floating cars.” Thisconcept of data collection presupposes wireless communications for datatransfer between the floating cars and a traffic center. Preferably,data transfer is carried out via radio. Due to the limited capacity ofthe broadcast channels, such communications must, for technical as wellas economic reasons, be limited, to the greatest possible extent, to thenecessary minimum. Instead of constantly maintaining radio contact, atypical application of the floating car concept disclosed, for examplein DE 195 13 640 simply transmits the most recent measurement data atregular intervals. These data include, in particular, the time of day,the location and speed of the vehicle and, as applicable, othermeasurement variables on the vehicle surroundings, e.g., fog, rain orblack ice. Such a chronological chain of individual data is describedhereinafter as the “driving profile.”

However, this known process is not completely satisfactory. It has thedisadvantage that, despite data reduction, measurement data with littleinformative value are frequently transmitted. The reporting behavior ofeach vehicle is controlled purely chronologically, for example, and isnot directly influenced by the usefulness of the transmitted data forthe purpose of traffic assessment. The individual floating cars reporttheir data regardless of whether they happen to be located on acompletely empty road or in heavy traffic or in a zone where traffic hasbeen disrupted by a recent accident. Since the primary goal of datacollection for traffic assessment is to detect traffic disruptions,reports of non-disrupted traffic contribute only slightly to this goal.

SUMMARY OF THE INVENTION

The object of the invention is to further develop a generic process insuch a way that data transmission from floating vehicles to a trafficcenter is limited to the greatest possible extent largely to data withgreat informative value for traffic assessment. Another object of theinvention is to provide a device to implement this process.

This object is attained according to the invention by a process forwireless transmission of data for traffic system assessment in segmentsof a road network to a traffic center, comprising the steps ofcollecting data using sensors in a floating vehicle in the road network,forming a current driving profile from the data, deriving actual valuesof characteristic driving profile properties from the current drivingprofile, forming expected values of characteristic driving profileproperties based on preestablished traffic situation information,comparing the actual values to the expected values, assessing adifference found in said step of comparing and determining whether thedifference is a serious deviation from the expected values based onpreestablished decision criteria, and transmitting the actual values tothe traffic center if it is determined that the difference is a seriousdeviation in said step of determining.

The object is also attained by a device for wireless transmission ofdata for traffic system assessment in segments of a road network to atraffic center, including a sensor system mounted in a floating vehiclefor determining driving profile data, a processing device for receivingthe driving profile data from said sensor system and determining actualvalues and expected values of characteristic driving profile properties,a comparator for comparing the actual values and expected values of thecharacteristic driving profile properties and determining a differencebetween said actual values and said expected values, a first memorycomprising decision criteria, and a transmitting device for transmittingsaid driving profile data to the traffic center when said differencebetween said actual values and said expected values is determined to bea serious deviation from said expected values based on said decisioncriteria in said first memory.

By means of the process according to the invention, the transmission ofredundant or irrelevant data is kept to a minimum. The starting point ofthe invention is the idea that data reflective of the picture of thetraffic situation that already exists (or probably exists) at a trafficcenter are not of interest in themselves and therefore, if possible,should not be transmitted by individual data collection vehicles. Thissituation must be objectively recognizable in the individual vehicles,so that an appropriate decision to transmit data or to refrain fromtransmitting data from each vehicle can be made.

The basis of the invention is the sensor data collected in a vehicle.These sensor data are collected cyclically, for example, then storedtemporarily and assessed in the vehicle. The totality of sensor datacreates a “driving profile.” In general terms, a driving profile is adescription of driving behavior over a certain route segment or acertain time period. Simple forms of driving profiles include: speedtravelled as a function of time (speed-time graph), location as afunction of time (location-time graph), and speed as a function oflocation. Of course, other sensor data, such as turning angle,acceleration, etc. can also be used for the driving profile. A drivingprofile has in fact been “driven” and describes the actual behavior ofthe vehicle.

According to the invention, a current driving profile is created fromthe sensor data collected in the vehicle. Then, in the vehicle,characteristic properties in the form of actual values are derived fromthat current driving profile. Further, based on predetermined trafficsituation information, characteristic driving profile properties in theform of expected values are also arrived at in the vehicle. In theframework of the invention, these expected values of the driving profileproperties are then compared with the actual values of the drivingprofile properties. After this, the differences found by means of thiscomparison are evaluated in the vehicle on the basis of preestablisheddecision criteria. Based on this evaluation, collected data aretransmitted to the traffic center only if required according to thedecision criteria.

In the sense of the present invention, the driving profile propertiesserve to summarize a driving profile in the form of a few criteria orcharacteristic values, so that this profile can then be checked, assimply as possible, for compatibility with a fictitious driving profilethat corresponds to the traffic situation existing according to trafficinformation that has been received. In the simplest case, for example,the average speed at a preestablished time or segment interval could beused as the characteristic property. The values of the lowest andhighest speeds in an interval (threshold values) are another propertythat could be assessed.

This means, for example, that a vehicle travelling in a route segmentwhere radio broadcasts have reported sluggish traffic assumes arelatively low speed as the expected value for the average speed. Thus,the actual speed of the vehicle should never be in a high range, andshould be zero only for very brief time periods, at the most. Were thesensor system of the vehicle to determine a high speed over a certaintime period or route segment, this would be evidence that the sluggishtraffic had cleared up. Conversely, a longer stop by the vehicle couldpoint to an accident. In both cases, the transmission of data to thetraffic center would be useful. In contrast, if the expected averagespeed actually existed, data transmission would not be useful.

When the transmitted traffic situation information also includes traveltimes between two points, for example, as various proposals havesuggested, the measured driving profile can be analyzed for the actualtravel time. It is also possible to measure the length of traffic jamsin this way, i.e., the measured driving profile can be analyzed todetermine the route segment over which the otherwise usual speed isreduced. In addition, more complex descriptions, such as “stop and go,”“clear,” etc., can constitute driving profile properties in the sense ofthe invention.

The decisive step of the invention is the formation of expected valuesfrom received traffic information, and the transmission of a report assoon as the vehicle discovers (i.e., measures) a different situationthan the one expected. Thus, the unique feature is that the vehicle now“knows” the traffic situation as pictured by the traffic center, andindependently ascertains the correctness—or particularly, theincorrectness—of this picture. In contrast, DE 19 13 640 A1 assigns thevehicle the role of sending traffic data to the traffic center, and onlythe traffic center “knows” the traffic situation. The result is thatvehicles function, for example, as “traffic jam detectors” and, uponentering a traffic jam, regularly report this event. This report isrepeated by each new “floating car” to enter the traffic jam. However,by then, the traffic jam information is already known to the trafficcenter. The present invention prevents the transmission of suchredundant information from the vehicle.

Current traffic information can, of course, also be transmitted to thevehicles other than by radio, e.g., by cellular mobile telephone underthe GSM standard. Especially preferred is the transmission ofinformation via a broadcast-capable radio network, particularly a pagingnetwork. It is also possible to create the expected values of thedriving profile properties based not on currently received data, butrather on predicted traffic situation data. For this purpose, heuristictraffic situation data can also be used as a basis. In this case, it isespecially advisable to modify and store the heuristic traffic situationdata for a given route segment in the vehicle, based on the collectedsensor data, in the manner of a self-learning system, so as to improveits informative value. At least the variables time of day, vehiclelocation and vehicle speed should be used as a basis to define thedriving profile. With respect to the decision criteria used in avehicle, it can be advantageous to predetermine these in a variablemanner from the outside. Thus, it is especially advantageous when thetraffic center that is to receive the data can transmit such decisioncriteria to vehicles (e.g., in a certain area) by means of wirelesscommunications, so that necessary changes can be made immediately,without individual vehicles having to stop at a workplace, for example,for such updates. Thus, in view of the decision process, it should bepossible to prescribe parameters for the user device in the vehicle;that is, the comparison criteria and the sensitivity of the decisionprocess should be predeterminable by the traffic center.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a device for wireless transmission ofdata for traffic system assessment in segments of a road network to atraffic center according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, the functionalities occurring in a vehicle 30 and the deviceslocated in the vehicle 30 are surrounded by a dashed line. These deviceslocated in the vehicle together make a device for transmitting data ontraffic assessment according to the present invention. Via a firstreceiver 42, the vehicle 30 can wirelessly receive traffic information15 that is broadcast, for example, via radio, broadcast service 10 orpager service. Preferably, the traffic information 15 is transmitted incoded form. For this purpose, various processes can be used, such, forexample, as ALERT-C. The origin of the traffic information 15, (whetherthis information is broadcast by a radio station or by a traffic centercollecting traffic data) is not of primary importance. The trafficinformation relevant to a segment just travelled by a vehicle forms a“traffic situation 44”. Predetermined conversion algorithms are used toderive from this information characteristic driving profile propertiesin the form of expected driving profile properties. In a simple form,the creation of characteristic driving profile properties may, forexample, include establishing a threshold value for speed. However,highly complex assumptions about typical driving profiles can also bemade. In the framework of the invention, it can be useful for theconversion algorithms to be preestablished by a traffic center 20 viawireless communication, so as to ensure uniform conversion in all“floating cars.” Further, a series of sensors 46, which can detectdriving-relevant measurement data, are located in the vehicle 30. As arule, these data include, along with the time of day, in particular, thespeed and current position of the vehicle 30. Preferably, the sensors 46include a locating device 46 a operating on the basis of satellitenavigation to determine the vehicle location. This locating device 46 amay be a direct component of the device provided to implement theinvention, or the device to implement the invention may be connected tosuch a locating device 46 a. From the current actual driving profile 50,which is formed via the chronological sequence of data from sensors 46,the device according to the invention derives 52. A processing device 65may include an integral circuit for determining the expected drivingprofile properties 48 and the actual driving profile properties 52;actual driving profile properties. The device further comprises acomparator 60, in which the actual driving profile properties 52 arecompared with the expected driving profile properties 48. To assess theresults of this comparison, suitable decision criteria 58 are suppliedto the comparator 60 from a memory 56. Depending on whether thecomparison by the comparator 60 leads to the conclusion that a seriousdeviation from the expected traffic situation does (or does not) exist,a report is (or is not) sent to the traffic center via a transmitter 64belonging to the device according to the invention. In the example, thedevice according to the invention also has a second receiver 54, whichcan receive modified decision criteria transmitted from the trafficcenter to the memory of the vehicle. Of course, it is also possible forthe first receiver 42 for traffic information and the second receiver 54for decision criteria to be physically one and the same receiver.

As mentioned above, it is not absolutely necessary to supply the vehiclewith current traffic information to arrive at the expected drivingprofile properties 48. For this purpose, for example, heuristicinformation could be stored in the vehicle 30 in static form. Suchheuristic systems can be presented in the form of load curves or similarmethods familiar to the expert, for example. An expected profiledependent on the time of day can then be derived. In principle, it isalso possible, for the purpose of refining the informative value, tomodify or update the heuristic information by maintenance from theoutside (preferably from the traffic center). Reference has already beenmade to the possibility of independent updating in the sense of aself-learning system.

In specific technical terms, the device according to the invention andthe process according to the invention can be embodied in the vehicle inmany different ways. For example, a device for vehicle navigation can beprovided in the vehicle, which navigation device, via asatellite-supported locating device and a digital road map stored, forexample, on CD-ROM and/or in memory 56 can exactly determine the currentlocation of the vehicle 30 and associate it with a certain segment ofthe road network. As a result, the device according to the inventionwould know, for example, that the vehicle is currently located “onAutobahn A3 between interchanges X and Y.” If the device according tothe invention receives traffic information with the contents “trafficjam on A3 between interchanges X and Y, 6 km in length,” thisinformation can be converted into a corresponding driving profile withcharacteristic properties. In this case, the vehicle will expect atypical stop-and-go traffic profile. If the relevant road segment on theA3 between interchanges X and Y has unexpectedly become clear, theactual vehicle speed should be higher and more uniform than the expectedvalues. The comparator 60 recognizes these deviations and can determine,based on the decision criteria, that the data of the actual drivingprofile should advantageously be transmitted to the traffic center 20,because the actual deviations are impermissibly high. In this relativelysimple way, it is possible to limit the scope of the data transmitted bya fleet of “floating cars” for traffic situation assessment to a trafficcenter to a relatively low level.

What is claimed is:
 1. A process for wireless transmission of data fortraffic system assessment in segments of a road network to a trafficcenter, comprising the steps of: collecting data using sensors in afloating vehicle in the road network; forming a current driving profilefrom the data; deriving actual values of characteristic driving profileproperties from the current driving profile; forming expected values ofcharacteristic driving profile properties based on preestablishedtraffic situation information; comparing the actual values to theexpected values; assessing a difference found in said step of comparingand determining whether the difference is a serious deviation from theexpected values based on preestablished decision criteria; andtransmitting the actual values to the traffic center if it is determinedthat the difference is a serious deviation in said step of determining.2. The process of claim 1, wherein said step of forming expected valuescomprises forming expected values based on traffic information receivedvia wireless communication.
 3. The process of claim 1, wherein said stepof forming expected values comprises forming expected values based onpredicted traffic situation data.
 4. The process of claim 1, whereinsaid step of forming expected values comprises forming expected valuesbased on heuristic traffic situation data.
 5. The process of claim 4,further comprising the steps of modifiying and storing the heuristictraffic situation data based on the data collected by the sensors of thefloating vehicle via a self-learning system.
 6. The process of claim 1,wherein said step of forming a current driving profile comprises forminga current driving profile including time, location and speed of thefloating vehicle.
 7. The process of claim 2, further comprising the stepof receiving the traffic information via a cellular mobile telephonenetwork.
 8. The process of claim 2, further comprising the step ofreceiving the traffic information via a broadcast-capable radio network.9. The process of claim 1, further comprising the step of changing thepreestablished decision criteria as required by the traffic center via awireless communication.
 10. A device for wireless transmission of datafor traffic system assessment in segments of a road network to a trafficcenter, including: a sensor system mounted in a floating vehicle fordetermining driving profile data; a processing device for receiving thedriving profile data from said sensor system and determining actualvalues and expected values of characteristic driving profile properties;a comparator for comparing the actual values and expected values of thecharacteristic driving profile properties and determining a differencebetween said actual values and said expected values; a first memorycomprising decision criteria; and a transmitting device for transmittingsaid driving profile data to the traffic center when said differencebetween said actual values and said expected values is determined to bea serious deviation from said expected values based on said decisioncriteria in said first memory.
 11. The device of claim 10, furthercomprising a first receiver for receiving current traffic informationfrom an external source and inputting said current traffic informationto the said processing device for use in determining said expectedvalues of characteristic driving profile properties.
 12. The device ofclaim 11, wherein said first receiver comprises a device for operationin a cellular mobile telephone network.
 13. The device of claim 11,wherein said first receiver comprises a device for operation in abroadcast-capable radio network.
 14. The device of claim 10, furthercomprising a second receiver for receiving said decision criteria fromthe traffic center and transmitting said decision criteria to saidmemory.
 15. The device of claim 10, further comprising a second memoryincluding a digital roadmap.
 16. The device of claim 15, furthercomprising a memory device, wherein said first memory and said secondmemory comprise portions of said memory drive.
 17. The device of claim10, wherein said sensor system further comprises a location device fordetermining a location of the floating vehicle.
 18. The device of claim17, wherein said location device comprises a device operable on thebasis of satellite navigation.